"He is not a mailman, he is an electrician."
Translation:El nu e poștaș, el este un electrician.
He=El, often we don't use that because it is faster and we understand each other if we omit "El", but literally correct is with El. I am a native and wrote "El nu este un poştaş" and it was wrong. I guess they can be translated the same, even if "a/an" from english is translated to an article in romanian.